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        Package&nbsp;pybindgen
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<h1 class="epydoc">Source Code for <a href="pybindgen-module.html">Package pybindgen</a></h1>
<pre class="py-src">
<a name="L1"></a><tt class="py-lineno">  1</tt>  <tt class="py-line"> </tt>
<a name="L2"></a><tt class="py-lineno">  2</tt>  <tt class="py-line"><tt class="py-docstring">"""</tt> </tt>
<a name="L3"></a><tt class="py-lineno">  3</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L4"></a><tt class="py-lineno">  4</tt>  <tt class="py-line"><tt class="py-docstring">What is pybindgen ?</tt> </tt>
<a name="L5"></a><tt class="py-lineno">  5</tt>  <tt class="py-line"><tt class="py-docstring">===================</tt> </tt>
<a name="L6"></a><tt class="py-lineno">  6</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L7"></a><tt class="py-lineno">  7</tt>  <tt class="py-line"><tt class="py-docstring">Pybindgen is a tool which can be used to generate python bindings</tt> </tt>
<a name="L8"></a><tt class="py-lineno">  8</tt>  <tt class="py-line"><tt class="py-docstring">for C or C++ APIs. It is similar in scope to tools such as boost::python,</tt> </tt>
<a name="L9"></a><tt class="py-lineno">  9</tt>  <tt class="py-line"><tt class="py-docstring">XXX, and a few others but has a number of specific features which make</tt> </tt>
<a name="L10"></a><tt class="py-lineno"> 10</tt>  <tt class="py-line"><tt class="py-docstring">it especially useful in a number of cases:</tt> </tt>
<a name="L11"></a><tt class="py-lineno"> 11</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L12"></a><tt class="py-lineno"> 12</tt>  <tt class="py-line"><tt class="py-docstring">  - pybindgen is implemented in python and is used and controlled through python</tt> </tt>
<a name="L13"></a><tt class="py-lineno"> 13</tt>  <tt class="py-line"><tt class="py-docstring">  - pybindgen error messages do not involve c++ template deciphering (think about</tt> </tt>
<a name="L14"></a><tt class="py-lineno"> 14</tt>  <tt class="py-line"><tt class="py-docstring">  boost::python)</tt> </tt>
<a name="L15"></a><tt class="py-lineno"> 15</tt>  <tt class="py-line"><tt class="py-docstring">  - pybindgen generates highly-readable C or C++ code so it is possible to step</tt> </tt>
<a name="L16"></a><tt class="py-lineno"> 16</tt>  <tt class="py-line"><tt class="py-docstring">  into and debug the bindings</tt> </tt>
<a name="L17"></a><tt class="py-lineno"> 17</tt>  <tt class="py-line"><tt class="py-docstring">  - In simple cases, pybindgen is really easy to use. In more complicated cases,</tt> </tt>
<a name="L18"></a><tt class="py-lineno"> 18</tt>  <tt class="py-line"><tt class="py-docstring">  it does offer all the flexibility you need to wrap complex C or C++ APIs.</tt> </tt>
<a name="L19"></a><tt class="py-lineno"> 19</tt>  <tt class="py-line"><tt class="py-docstring">  - pybindgen also provides an optional tool to parse C and C++ headers and generate</tt> </tt>
<a name="L20"></a><tt class="py-lineno"> 20</tt>  <tt class="py-line"><tt class="py-docstring">  automatically bindings for them, potentially using extra inline or out-of-line annotations. </tt> </tt>
<a name="L21"></a><tt class="py-lineno"> 21</tt>  <tt class="py-line"><tt class="py-docstring">  This tool is based on gccxml and pygccxml: it can be used to generate the first version of </tt> </tt>
<a name="L22"></a><tt class="py-lineno"> 22</tt>  <tt class="py-line"><tt class="py-docstring">  the bindings and tweak them by hand later or as a fully automated tool to continuously </tt> </tt>
<a name="L23"></a><tt class="py-lineno"> 23</tt>  <tt class="py-line"><tt class="py-docstring">  generate bindings for changing C/C++ APIs.</tt> </tt>
<a name="L24"></a><tt class="py-lineno"> 24</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L25"></a><tt class="py-lineno"> 25</tt>  <tt class="py-line"><tt class="py-docstring">This tutorial will show how to build bindings for a couple of common C and C++ API idioms</tt> </tt>
<a name="L26"></a><tt class="py-lineno"> 26</tt>  <tt class="py-line"><tt class="py-docstring">and, then, will proceed to show how to use the automatic binding generator.</tt> </tt>
<a name="L27"></a><tt class="py-lineno"> 27</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L28"></a><tt class="py-lineno"> 28</tt>  <tt class="py-line"><tt class="py-docstring">A simple example</tt> </tt>
<a name="L29"></a><tt class="py-lineno"> 29</tt>  <tt class="py-line"><tt class="py-docstring">================</tt> </tt>
<a name="L30"></a><tt class="py-lineno"> 30</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L31"></a><tt class="py-lineno"> 31</tt>  <tt class="py-line"><tt class="py-docstring">The best way to get a feel for what pybindgen looks like is to go through a </tt> </tt>
<a name="L32"></a><tt class="py-lineno"> 32</tt>  <tt class="py-line"><tt class="py-docstring">simple example. Let's assume that we have a simple C API as shown below</tt> </tt>
<a name="L33"></a><tt class="py-lineno"> 33</tt>  <tt class="py-line"><tt class="py-docstring">declared in a header my-module.h::</tt> </tt>
<a name="L34"></a><tt class="py-lineno"> 34</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L35"></a><tt class="py-lineno"> 35</tt>  <tt class="py-line"><tt class="py-docstring">  void MyModuleDoAction (void);</tt> </tt>
<a name="L36"></a><tt class="py-lineno"> 36</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L37"></a><tt class="py-lineno"> 37</tt>  <tt class="py-line"><tt class="py-docstring">What we want to do is call this C function from python and be able to write </tt> </tt>
<a name="L38"></a><tt class="py-lineno"> 38</tt>  <tt class="py-line"><tt class="py-docstring">python code such as:::</tt> </tt>
<a name="L39"></a><tt class="py-lineno"> 39</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L40"></a><tt class="py-lineno"> 40</tt>  <tt class="py-line"><tt class="py-docstring">  import MyModule</tt> </tt>
<a name="L41"></a><tt class="py-lineno"> 41</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L42"></a><tt class="py-lineno"> 42</tt>  <tt class="py-line"><tt class="py-docstring">  MyModule.MyModuleDoAction ()</tt> </tt>
<a name="L43"></a><tt class="py-lineno"> 43</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L44"></a><tt class="py-lineno"> 44</tt>  <tt class="py-line"><tt class="py-docstring">Getting there is, hopefully, not very complicated: we just need to write a small</tt> </tt>
<a name="L45"></a><tt class="py-lineno"> 45</tt>  <tt class="py-line"><tt class="py-docstring">python program whose job is to generate the C code which will act as a bridge</tt> </tt>
<a name="L46"></a><tt class="py-lineno"> 46</tt>  <tt class="py-line"><tt class="py-docstring">between our user's python program and the underlying C function. First, we import</tt> </tt>
<a name="L47"></a><tt class="py-lineno"> 47</tt>  <tt class="py-line"><tt class="py-docstring">the pybindgen and the sys modules:::</tt> </tt>
<a name="L48"></a><tt class="py-lineno"> 48</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L49"></a><tt class="py-lineno"> 49</tt>  <tt class="py-line"><tt class="py-docstring">  import pybindgen</tt> </tt>
<a name="L50"></a><tt class="py-lineno"> 50</tt>  <tt class="py-line"><tt class="py-docstring">  import sys</tt> </tt>
<a name="L51"></a><tt class="py-lineno"> 51</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L52"></a><tt class="py-lineno"> 52</tt>  <tt class="py-line"><tt class="py-docstring">Then, we create an object to represent the module we want to generate:::</tt> </tt>
<a name="L53"></a><tt class="py-lineno"> 53</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L54"></a><tt class="py-lineno"> 54</tt>  <tt class="py-line"><tt class="py-docstring">  mod = pybindgen.Module('MyModule')</tt> </tt>
<a name="L55"></a><tt class="py-lineno"> 55</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L56"></a><tt class="py-lineno"> 56</tt>  <tt class="py-line"><tt class="py-docstring">add our C header:::</tt> </tt>
<a name="L57"></a><tt class="py-lineno"> 57</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L58"></a><tt class="py-lineno"> 58</tt>  <tt class="py-line"><tt class="py-docstring">  mod.add_include('"my-module.h"')</tt> </tt>
<a name="L59"></a><tt class="py-lineno"> 59</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L60"></a><tt class="py-lineno"> 60</tt>  <tt class="py-line"><tt class="py-docstring">and register our function which returns no value (hence, the second</tt> </tt>
<a name="L61"></a><tt class="py-lineno"> 61</tt>  <tt class="py-line"><tt class="py-docstring">argument 'None'), and, takes no arguments (hence, the third argument,</tt> </tt>
<a name="L62"></a><tt class="py-lineno"> 62</tt>  <tt class="py-line"><tt class="py-docstring">the empty list '[]'):::</tt> </tt>
<a name="L63"></a><tt class="py-lineno"> 63</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L64"></a><tt class="py-lineno"> 64</tt>  <tt class="py-line"><tt class="py-docstring">  mod.add_function('MyModuleDoAction', None, [])</tt> </tt>
<a name="L65"></a><tt class="py-lineno"> 65</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L66"></a><tt class="py-lineno"> 66</tt>  <tt class="py-line"><tt class="py-docstring">Finally, we generate code for this binding directed to standard output:::</tt> </tt>
<a name="L67"></a><tt class="py-lineno"> 67</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L68"></a><tt class="py-lineno"> 68</tt>  <tt class="py-line"><tt class="py-docstring">  mod.generate(sys.stdout)</tt> </tt>
<a name="L69"></a><tt class="py-lineno"> 69</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L70"></a><tt class="py-lineno"> 70</tt>  <tt class="py-line"><tt class="py-docstring">The final program is pretty short:::</tt> </tt>
<a name="L71"></a><tt class="py-lineno"> 71</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L72"></a><tt class="py-lineno"> 72</tt>  <tt class="py-line"><tt class="py-docstring">  import pybindgen</tt> </tt>
<a name="L73"></a><tt class="py-lineno"> 73</tt>  <tt class="py-line"><tt class="py-docstring">  import sys</tt> </tt>
<a name="L74"></a><tt class="py-lineno"> 74</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L75"></a><tt class="py-lineno"> 75</tt>  <tt class="py-line"><tt class="py-docstring">  mod = pybindgen.Module('MyModule')</tt> </tt>
<a name="L76"></a><tt class="py-lineno"> 76</tt>  <tt class="py-line"><tt class="py-docstring">  mod.add_include('"my-module.h"')</tt> </tt>
<a name="L77"></a><tt class="py-lineno"> 77</tt>  <tt class="py-line"><tt class="py-docstring">  mod.add_function('MyModuleDoAction', None, [])</tt> </tt>
<a name="L78"></a><tt class="py-lineno"> 78</tt>  <tt class="py-line"><tt class="py-docstring">  mod.generate(sys.stdout)</tt> </tt>
<a name="L79"></a><tt class="py-lineno"> 79</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L80"></a><tt class="py-lineno"> 80</tt>  <tt class="py-line"><tt class="py-docstring">This very small example is located in the</tt> </tt>
<a name="L81"></a><tt class="py-lineno"> 81</tt>  <tt class="py-line"><tt class="py-docstring">U{tutorial/first-example&lt;http://pybindgen.googlecode.com/svn/trunk/tutorial/&gt;}</tt> </tt>
<a name="L82"></a><tt class="py-lineno"> 82</tt>  <tt class="py-line"><tt class="py-docstring">directory together with a small makefile which will build our small C</tt> </tt>
<a name="L83"></a><tt class="py-lineno"> 83</tt>  <tt class="py-line"><tt class="py-docstring">library, the bridging code, and a python module:::</tt> </tt>
<a name="L84"></a><tt class="py-lineno"> 84</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L85"></a><tt class="py-lineno"> 85</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen$ cd tutorial/first-example/</tt> </tt>
<a name="L86"></a><tt class="py-lineno"> 86</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen/tutorial/first-example$ make</tt> </tt>
<a name="L87"></a><tt class="py-lineno"> 87</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -fPIC -c -o my-module.o my-module.c</tt> </tt>
<a name="L88"></a><tt class="py-lineno"> 88</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -shared -o libmymodule.so my-module.o</tt> </tt>
<a name="L89"></a><tt class="py-lineno"> 89</tt>  <tt class="py-line"><tt class="py-docstring">  PYTHONPATH=$PYTHONPATH:../../ python my-module.py &gt; my-module-binding.c</tt> </tt>
<a name="L90"></a><tt class="py-lineno"> 90</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -fPIC -I/usr/include/python2.5 -c -o my-module-binding.o my-module-binding.c</tt> </tt>
<a name="L91"></a><tt class="py-lineno"> 91</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -shared -o MyModule.so -L. -lmymodule my-module-binding.o</tt> </tt>
<a name="L92"></a><tt class="py-lineno"> 92</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen/tutorial/first-example$ </tt> </tt>
<a name="L93"></a><tt class="py-lineno"> 93</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L94"></a><tt class="py-lineno"> 94</tt>  <tt class="py-line"><tt class="py-docstring">The first two lines are simply used to build our example C library in </tt> </tt>
<a name="L95"></a><tt class="py-lineno"> 95</tt>  <tt class="py-line"><tt class="py-docstring">libmymodule.so so, these are not very interesting. The more interesting bit</tt> </tt>
<a name="L96"></a><tt class="py-lineno"> 96</tt>  <tt class="py-line"><tt class="py-docstring">starts with:::</tt> </tt>
<a name="L97"></a><tt class="py-lineno"> 97</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L98"></a><tt class="py-lineno"> 98</tt>  <tt class="py-line"><tt class="py-docstring">  PYTHONPATH=$PYTHONPATH:../../ python my-module.py &gt; my-module-binding.c</tt> </tt>
<a name="L99"></a><tt class="py-lineno"> 99</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L100"></a><tt class="py-lineno">100</tt>  <tt class="py-line"><tt class="py-docstring">which is just a fancy way to run our binding generator program while</tt> </tt>
<a name="L101"></a><tt class="py-lineno">101</tt>  <tt class="py-line"><tt class="py-docstring">ensuring that it will find the pybindgen module and while dumping the output</tt> </tt>
<a name="L102"></a><tt class="py-lineno">102</tt>  <tt class="py-line"><tt class="py-docstring">of the program to the file named my-module-binding.c. This file is then build</tt> </tt>
<a name="L103"></a><tt class="py-lineno">103</tt>  <tt class="py-line"><tt class="py-docstring">and linked into a python module:::</tt> </tt>
<a name="L104"></a><tt class="py-lineno">104</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L105"></a><tt class="py-lineno">105</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -fPIC -I/usr/include/python2.5 -c -o my-module-binding.o my-module-binding.c</tt> </tt>
<a name="L106"></a><tt class="py-lineno">106</tt>  <tt class="py-line"><tt class="py-docstring">  gcc -shared -o MyModule.so -L. -lmymodule my-module-binding.o</tt> </tt>
<a name="L107"></a><tt class="py-lineno">107</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L108"></a><tt class="py-lineno">108</tt>  <tt class="py-line"><tt class="py-docstring">Once all of that code is built, we obviously want to run it. Setting up</tt> </tt>
<a name="L109"></a><tt class="py-lineno">109</tt>  <tt class="py-line"><tt class="py-docstring">your system to make sure that the python module is found by the python runtime</tt> </tt>
<a name="L110"></a><tt class="py-lineno">110</tt>  <tt class="py-line"><tt class="py-docstring">is outside the scope of this tutorial but, for most people, the following session</tt> </tt>
<a name="L111"></a><tt class="py-lineno">111</tt>  <tt class="py-line"><tt class="py-docstring">should be self-explanatory:::</tt> </tt>
<a name="L112"></a><tt class="py-lineno">112</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L113"></a><tt class="py-lineno">113</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen/tutorial/first-example$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:.</tt> </tt>
<a name="L114"></a><tt class="py-lineno">114</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen/tutorial/first-example$ export PYTHONPATH=$PYTHONPATH:.</tt> </tt>
<a name="L115"></a><tt class="py-lineno">115</tt>  <tt class="py-line"><tt class="py-docstring">  mathieu@ns-test:~/code/pybindgen/tutorial/first-example$ python</tt> </tt>
<a name="L116"></a><tt class="py-lineno">116</tt>  <tt class="py-line"><tt class="py-docstring">  Python 2.5.1 (r251:54863, Mar  7 2008, 03:39:23) </tt> </tt>
<a name="L117"></a><tt class="py-lineno">117</tt>  <tt class="py-line"><tt class="py-docstring">  [GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2</tt> </tt>
<a name="L118"></a><tt class="py-lineno">118</tt>  <tt class="py-line"><tt class="py-docstring">  Type "help", "copyright", "credits" or "license" for more information.</tt> </tt>
<a name="L119"></a><tt class="py-lineno">119</tt>  <tt class="py-line"><tt class="py-docstring">  &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L120"></a><tt class="py-lineno">120</tt>  <tt class="py-line"><tt class="py-docstring">  &gt;&gt;&gt; MyModule.MyModuleDoAction ()</tt> </tt>
<a name="L121"></a><tt class="py-lineno">121</tt>  <tt class="py-line"><tt class="py-docstring">  You called MyModuleDoAction !</tt> </tt>
<a name="L122"></a><tt class="py-lineno">122</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L123"></a><tt class="py-lineno">123</tt>  <tt class="py-line"><tt class="py-docstring">Wrapping types by value</tt> </tt>
<a name="L124"></a><tt class="py-lineno">124</tt>  <tt class="py-line"><tt class="py-docstring">=======================</tt> </tt>
<a name="L125"></a><tt class="py-lineno">125</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L126"></a><tt class="py-lineno">126</tt>  <tt class="py-line"><tt class="py-docstring">  Primitive types</tt> </tt>
<a name="L127"></a><tt class="py-lineno">127</tt>  <tt class="py-line"><tt class="py-docstring">  ---------------</tt> </tt>
<a name="L128"></a><tt class="py-lineno">128</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L129"></a><tt class="py-lineno">129</tt>  <tt class="py-line"><tt class="py-docstring">  The first example showed how to call a function which takes no</tt> </tt>
<a name="L130"></a><tt class="py-lineno">130</tt>  <tt class="py-line"><tt class="py-docstring">  arguments and returns no values which, obviously, is not especially</tt> </tt>
<a name="L131"></a><tt class="py-lineno">131</tt>  <tt class="py-line"><tt class="py-docstring">  interesting so, let's look at how we can give meaningfull arguments</tt> </tt>
<a name="L132"></a><tt class="py-lineno">132</tt>  <tt class="py-line"><tt class="py-docstring">  to our function::</tt> </tt>
<a name="L133"></a><tt class="py-lineno">133</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L134"></a><tt class="py-lineno">134</tt>  <tt class="py-line"><tt class="py-docstring">    int MyModuleDoAction (int v1, int v2);</tt> </tt>
<a name="L135"></a><tt class="py-lineno">135</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L136"></a><tt class="py-lineno">136</tt>  <tt class="py-line"><tt class="py-docstring">  and the corresponding bit from the code generation script: the second</tt> </tt>
<a name="L137"></a><tt class="py-lineno">137</tt>  <tt class="py-line"><tt class="py-docstring">  argument to add_function specifies that our function returns a value of type</tt> </tt>
<a name="L138"></a><tt class="py-lineno">138</tt>  <tt class="py-line"><tt class="py-docstring">  'int' and the third argument specifies that our function takes as a</tt> </tt>
<a name="L139"></a><tt class="py-lineno">139</tt>  <tt class="py-line"><tt class="py-docstring">  single argument an 'int' of name 'value':::</tt> </tt>
<a name="L140"></a><tt class="py-lineno">140</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L141"></a><tt class="py-lineno">141</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_function('MyModuleDoAction', </tt> </tt>
<a name="L142"></a><tt class="py-lineno">142</tt>  <tt class="py-line"><tt class="py-docstring">                      pybindgen.retval ('int'), </tt> </tt>
<a name="L143"></a><tt class="py-lineno">143</tt>  <tt class="py-line"><tt class="py-docstring">                     [pybindgen.param ('int', 'v1'),</tt> </tt>
<a name="L144"></a><tt class="py-lineno">144</tt>  <tt class="py-line"><tt class="py-docstring">                      pybindgen.param ('int', 'v2')])</tt> </tt>
<a name="L145"></a><tt class="py-lineno">145</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L146"></a><tt class="py-lineno">146</tt>  <tt class="py-line"><tt class="py-docstring">  The above then allows you to write:</tt> </tt>
<a name="L147"></a><tt class="py-lineno">147</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L148"></a><tt class="py-lineno">148</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L149"></a><tt class="py-lineno">149</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; v = MyModule.MyModuleDoAction (10, -1)</tt> </tt>
<a name="L150"></a><tt class="py-lineno">150</tt>  <tt class="py-line"><tt class="py-docstring">    You called MyModuleDoAction: 10</tt> </tt>
<a name="L151"></a><tt class="py-lineno">151</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v</tt> </tt>
<a name="L152"></a><tt class="py-lineno">152</tt>  <tt class="py-line"><tt class="py-docstring">    10</tt> </tt>
<a name="L153"></a><tt class="py-lineno">153</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; v = MyModule.MyModuleDoAction (v2=5, v1=-2)</tt> </tt>
<a name="L154"></a><tt class="py-lineno">154</tt>  <tt class="py-line"><tt class="py-docstring">    You called MyModuleDoAction: -2</tt> </tt>
<a name="L155"></a><tt class="py-lineno">155</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v</tt> </tt>
<a name="L156"></a><tt class="py-lineno">156</tt>  <tt class="py-line"><tt class="py-docstring">    -2</tt> </tt>
<a name="L157"></a><tt class="py-lineno">157</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L158"></a><tt class="py-lineno">158</tt>  <tt class="py-line"><tt class="py-docstring">  Which shows how the argument name can be used to avoid</tt> </tt>
<a name="L159"></a><tt class="py-lineno">159</tt>  <tt class="py-line"><tt class="py-docstring">  using positional arguments.</tt> </tt>
<a name="L160"></a><tt class="py-lineno">160</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L161"></a><tt class="py-lineno">161</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L162"></a><tt class="py-lineno">162</tt>  <tt class="py-line"><tt class="py-docstring">  Of course, the above example could be rewritten to the more compact and readable:::</tt> </tt>
<a name="L163"></a><tt class="py-lineno">163</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L164"></a><tt class="py-lineno">164</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import *</tt> </tt>
<a name="L165"></a><tt class="py-lineno">165</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_function('MyModuleDoAction', retval ('int'), </tt> </tt>
<a name="L166"></a><tt class="py-lineno">166</tt>  <tt class="py-line"><tt class="py-docstring">                     [param ('int', 'v1'),</tt> </tt>
<a name="L167"></a><tt class="py-lineno">167</tt>  <tt class="py-line"><tt class="py-docstring">                      param ('int', 'v2')])</tt> </tt>
<a name="L168"></a><tt class="py-lineno">168</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L169"></a><tt class="py-lineno">169</tt>  <tt class="py-line"><tt class="py-docstring">  In the following examples, this is what we will do to avoid extra typing.</tt> </tt>
<a name="L170"></a><tt class="py-lineno">170</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L171"></a><tt class="py-lineno">171</tt>  <tt class="py-line"><tt class="py-docstring">  Enum types</tt> </tt>
<a name="L172"></a><tt class="py-lineno">172</tt>  <tt class="py-line"><tt class="py-docstring">  ----------</tt> </tt>
<a name="L173"></a><tt class="py-lineno">173</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L174"></a><tt class="py-lineno">174</tt>  <tt class="py-line"><tt class="py-docstring">  Enums are often used to define C and C++ constants as shown below:::</tt> </tt>
<a name="L175"></a><tt class="py-lineno">175</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L176"></a><tt class="py-lineno">176</tt>  <tt class="py-line"><tt class="py-docstring">    enum MyEnum_e</tt> </tt>
<a name="L177"></a><tt class="py-lineno">177</tt>  <tt class="py-line"><tt class="py-docstring">    {</tt> </tt>
<a name="L178"></a><tt class="py-lineno">178</tt>  <tt class="py-line"><tt class="py-docstring">      CONSTANT_A,</tt> </tt>
<a name="L179"></a><tt class="py-lineno">179</tt>  <tt class="py-line"><tt class="py-docstring">      CONSTANT_B,</tt> </tt>
<a name="L180"></a><tt class="py-lineno">180</tt>  <tt class="py-line"><tt class="py-docstring">      CONSTANT_C</tt> </tt>
<a name="L181"></a><tt class="py-lineno">181</tt>  <tt class="py-line"><tt class="py-docstring">    };</tt> </tt>
<a name="L182"></a><tt class="py-lineno">182</tt>  <tt class="py-line"><tt class="py-docstring">    void MyModuleDoAction (enum enum_e value);</tt> </tt>
<a name="L183"></a><tt class="py-lineno">183</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L184"></a><tt class="py-lineno">184</tt>  <tt class="py-line"><tt class="py-docstring">  And wrapping them is also pretty trivial:::</tt> </tt>
<a name="L185"></a><tt class="py-lineno">185</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L186"></a><tt class="py-lineno">186</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import *</tt> </tt>
<a name="L187"></a><tt class="py-lineno">187</tt>  <tt class="py-line"><tt class="py-docstring">    import sys</tt> </tt>
<a name="L188"></a><tt class="py-lineno">188</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L189"></a><tt class="py-lineno">189</tt>  <tt class="py-line"><tt class="py-docstring">    mod = Module('MyModule')</tt> </tt>
<a name="L190"></a><tt class="py-lineno">190</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_include('"my-module.h"')</tt> </tt>
<a name="L191"></a><tt class="py-lineno">191</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_enum('MyEnum_e', ['CONSTANT_A', 'CONSTANT_B', 'CONSTANT_C'])</tt> </tt>
<a name="L192"></a><tt class="py-lineno">192</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_function('MyModuleDoAction', None, [param('MyEnum_e', 'value')])</tt> </tt>
<a name="L193"></a><tt class="py-lineno">193</tt>  <tt class="py-line"><tt class="py-docstring">    mod.generate(sys.stdout)</tt> </tt>
<a name="L194"></a><tt class="py-lineno">194</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L195"></a><tt class="py-lineno">195</tt>  <tt class="py-line"><tt class="py-docstring">  With the resulting python-visible API:</tt> </tt>
<a name="L196"></a><tt class="py-lineno">196</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L197"></a><tt class="py-lineno">197</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L198"></a><tt class="py-lineno">198</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print MyModule.CONSTANT_A</tt> </tt>
<a name="L199"></a><tt class="py-lineno">199</tt>  <tt class="py-line"><tt class="py-docstring">    0</tt> </tt>
<a name="L200"></a><tt class="py-lineno">200</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print MyModule.CONSTANT_B</tt> </tt>
<a name="L201"></a><tt class="py-lineno">201</tt>  <tt class="py-line"><tt class="py-docstring">    1</tt> </tt>
<a name="L202"></a><tt class="py-lineno">202</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print MyModule.CONSTANT_C</tt> </tt>
<a name="L203"></a><tt class="py-lineno">203</tt>  <tt class="py-line"><tt class="py-docstring">    2</tt> </tt>
<a name="L204"></a><tt class="py-lineno">204</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; MyModule.MyModuleDoAction (MyModule.CONSTANT_B)</tt> </tt>
<a name="L205"></a><tt class="py-lineno">205</tt>  <tt class="py-line"><tt class="py-docstring">    MyModuleDoAction: 1</tt> </tt>
<a name="L206"></a><tt class="py-lineno">206</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L207"></a><tt class="py-lineno">207</tt>  <tt class="py-line"><tt class="py-docstring">  Compound types</tt> </tt>
<a name="L208"></a><tt class="py-lineno">208</tt>  <tt class="py-line"><tt class="py-docstring">  --------------</tt> </tt>
<a name="L209"></a><tt class="py-lineno">209</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L210"></a><tt class="py-lineno">210</tt>  <tt class="py-line"><tt class="py-docstring">  Passing a structure to and from C is not really more complicated than</tt> </tt>
<a name="L211"></a><tt class="py-lineno">211</tt>  <tt class="py-line"><tt class="py-docstring">  our previous example. The API below:::</tt> </tt>
<a name="L212"></a><tt class="py-lineno">212</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L213"></a><tt class="py-lineno">213</tt>  <tt class="py-line"><tt class="py-docstring">    struct MyModuleStruct</tt> </tt>
<a name="L214"></a><tt class="py-lineno">214</tt>  <tt class="py-line"><tt class="py-docstring">    {</tt> </tt>
<a name="L215"></a><tt class="py-lineno">215</tt>  <tt class="py-line"><tt class="py-docstring">      int a;</tt> </tt>
<a name="L216"></a><tt class="py-lineno">216</tt>  <tt class="py-line"><tt class="py-docstring">      int b;</tt> </tt>
<a name="L217"></a><tt class="py-lineno">217</tt>  <tt class="py-line"><tt class="py-docstring">    };</tt> </tt>
<a name="L218"></a><tt class="py-lineno">218</tt>  <tt class="py-line"><tt class="py-docstring">    struct MyModuleStruct MyModuleDoAction (struct MyModuleStruct value);</tt> </tt>
<a name="L219"></a><tt class="py-lineno">219</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L220"></a><tt class="py-lineno">220</tt>  <tt class="py-line"><tt class="py-docstring">  can be bound to python using the following script:::</tt> </tt>
<a name="L221"></a><tt class="py-lineno">221</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L222"></a><tt class="py-lineno">222</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import *</tt> </tt>
<a name="L223"></a><tt class="py-lineno">223</tt>  <tt class="py-line"><tt class="py-docstring">    import sys</tt> </tt>
<a name="L224"></a><tt class="py-lineno">224</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L225"></a><tt class="py-lineno">225</tt>  <tt class="py-line"><tt class="py-docstring">    mod = Module('MyModule')</tt> </tt>
<a name="L226"></a><tt class="py-lineno">226</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_include('"my-module.h"')</tt> </tt>
<a name="L227"></a><tt class="py-lineno">227</tt>  <tt class="py-line"><tt class="py-docstring">    struct = mod.add_struct('MyModuleStruct')</tt> </tt>
<a name="L228"></a><tt class="py-lineno">228</tt>  <tt class="py-line"><tt class="py-docstring">    struct.add_instance_attribute('a', 'int')</tt> </tt>
<a name="L229"></a><tt class="py-lineno">229</tt>  <tt class="py-line"><tt class="py-docstring">    struct.add_instance_attribute('b', 'int')</tt> </tt>
<a name="L230"></a><tt class="py-lineno">230</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_function('MyModuleDoAction', retval ('MyModuleStruct'), [param ('MyModuleStruct', 'value')])</tt> </tt>
<a name="L231"></a><tt class="py-lineno">231</tt>  <tt class="py-line"><tt class="py-docstring">    mod.generate(sys.stdout)</tt> </tt>
<a name="L232"></a><tt class="py-lineno">232</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L233"></a><tt class="py-lineno">233</tt>  <tt class="py-line"><tt class="py-docstring">  The most obvious change here is that we have to define the new structure type:::</tt> </tt>
<a name="L234"></a><tt class="py-lineno">234</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L235"></a><tt class="py-lineno">235</tt>  <tt class="py-line"><tt class="py-docstring">    struct = mod.add_struct('MyModuleStruct')</tt> </tt>
<a name="L236"></a><tt class="py-lineno">236</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L237"></a><tt class="py-lineno">237</tt>  <tt class="py-line"><tt class="py-docstring">  and register the names and types of each of the members we want to make accessible</tt> </tt>
<a name="L238"></a><tt class="py-lineno">238</tt>  <tt class="py-line"><tt class="py-docstring">  from python:::</tt> </tt>
<a name="L239"></a><tt class="py-lineno">239</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L240"></a><tt class="py-lineno">240</tt>  <tt class="py-line"><tt class="py-docstring">    struct.add_instance_attribute('a', 'int')</tt> </tt>
<a name="L241"></a><tt class="py-lineno">241</tt>  <tt class="py-line"><tt class="py-docstring">    struct.add_instance_attribute('b', 'int')</tt> </tt>
<a name="L242"></a><tt class="py-lineno">242</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L243"></a><tt class="py-lineno">243</tt>  <tt class="py-line"><tt class="py-docstring">  The name of the method called here, 'add_instance_attribute' reflects the fact that</tt> </tt>
<a name="L244"></a><tt class="py-lineno">244</tt>  <tt class="py-line"><tt class="py-docstring">  pybindgen can wrap both C and C++ APIs: in C++, there exist both instance and static</tt> </tt>
<a name="L245"></a><tt class="py-lineno">245</tt>  <tt class="py-line"><tt class="py-docstring">  members so, pybindgen provides two methods: add_instance_attribute and add_static_attribute</tt> </tt>
<a name="L246"></a><tt class="py-lineno">246</tt>  <tt class="py-line"><tt class="py-docstring">  to register these two kinds of members.</tt> </tt>
<a name="L247"></a><tt class="py-lineno">247</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L248"></a><tt class="py-lineno">248</tt>  <tt class="py-line"><tt class="py-docstring">  Our C API then becomes accessible from python:</tt> </tt>
<a name="L249"></a><tt class="py-lineno">249</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L250"></a><tt class="py-lineno">250</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; st = MyModule.MyModuleStruct ()</tt> </tt>
<a name="L251"></a><tt class="py-lineno">251</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; st.a = 10</tt> </tt>
<a name="L252"></a><tt class="py-lineno">252</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; st.b = -20</tt> </tt>
<a name="L253"></a><tt class="py-lineno">253</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; st.c = -10</tt> </tt>
<a name="L254"></a><tt class="py-lineno">254</tt>  <tt class="py-line"><tt class="py-docstring">    Traceback (most recent call last):</tt> </tt>
<a name="L255"></a><tt class="py-lineno">255</tt>  <tt class="py-line"><tt class="py-docstring">      File "&lt;stdin&gt;", line 1, in &lt;module&gt;</tt> </tt>
<a name="L256"></a><tt class="py-lineno">256</tt>  <tt class="py-line"><tt class="py-docstring">    AttributeError: 'MyModule.MyModuleStruct' object has no attribute 'c'</tt> </tt>
<a name="L257"></a><tt class="py-lineno">257</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; v = MyModule.MyModuleDoAction (st)</tt> </tt>
<a name="L258"></a><tt class="py-lineno">258</tt>  <tt class="py-line"><tt class="py-docstring">    You called MyModuleDoAction: 10</tt> </tt>
<a name="L259"></a><tt class="py-lineno">259</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v</tt> </tt>
<a name="L260"></a><tt class="py-lineno">260</tt>  <tt class="py-line"><tt class="py-docstring">    &lt;MyModule.MyModuleStruct object at 0x2b5ef522b150&gt;</tt> </tt>
<a name="L261"></a><tt class="py-lineno">261</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v.a</tt> </tt>
<a name="L262"></a><tt class="py-lineno">262</tt>  <tt class="py-line"><tt class="py-docstring">    10</tt> </tt>
<a name="L263"></a><tt class="py-lineno">263</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v.b</tt> </tt>
<a name="L264"></a><tt class="py-lineno">264</tt>  <tt class="py-line"><tt class="py-docstring">    -20</tt> </tt>
<a name="L265"></a><tt class="py-lineno">265</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L266"></a><tt class="py-lineno">266</tt>  <tt class="py-line"><tt class="py-docstring">  C++ classes</tt> </tt>
<a name="L267"></a><tt class="py-lineno">267</tt>  <tt class="py-line"><tt class="py-docstring">  -----------</tt> </tt>
<a name="L268"></a><tt class="py-lineno">268</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L269"></a><tt class="py-lineno">269</tt>  <tt class="py-line"><tt class="py-docstring">  Wrapping C++ classes is very similar to wrapping a C struct with a few functions: we will thus</tt> </tt>
<a name="L270"></a><tt class="py-lineno">270</tt>  <tt class="py-line"><tt class="py-docstring">  start by extending our C API with a C++ class declaration:::</tt> </tt>
<a name="L271"></a><tt class="py-lineno">271</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L272"></a><tt class="py-lineno">272</tt>  <tt class="py-line"><tt class="py-docstring">    class MyClass</tt> </tt>
<a name="L273"></a><tt class="py-lineno">273</tt>  <tt class="py-line"><tt class="py-docstring">    {</tt> </tt>
<a name="L274"></a><tt class="py-lineno">274</tt>  <tt class="py-line"><tt class="py-docstring">    public:</tt> </tt>
<a name="L275"></a><tt class="py-lineno">275</tt>  <tt class="py-line"><tt class="py-docstring">      void SetInt (int value);</tt> </tt>
<a name="L276"></a><tt class="py-lineno">276</tt>  <tt class="py-line"><tt class="py-docstring">      int GetInt (void) const;</tt> </tt>
<a name="L277"></a><tt class="py-lineno">277</tt>  <tt class="py-line"><tt class="py-docstring">    };</tt> </tt>
<a name="L278"></a><tt class="py-lineno">278</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L279"></a><tt class="py-lineno">279</tt>  <tt class="py-line"><tt class="py-docstring">  We first need to declare a C++ class:::</tt> </tt>
<a name="L280"></a><tt class="py-lineno">280</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L281"></a><tt class="py-lineno">281</tt>  <tt class="py-line"><tt class="py-docstring">    mod = Module('MyModule')</tt> </tt>
<a name="L282"></a><tt class="py-lineno">282</tt>  <tt class="py-line"><tt class="py-docstring">    klass = mod.add_class('MyClass')</tt> </tt>
<a name="L283"></a><tt class="py-lineno">283</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L284"></a><tt class="py-lineno">284</tt>  <tt class="py-line"><tt class="py-docstring">  and, then, specify that it has a constructor:::</tt> </tt>
<a name="L285"></a><tt class="py-lineno">285</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L286"></a><tt class="py-lineno">286</tt>  <tt class="py-line"><tt class="py-docstring">    klass.add_constructor([])</tt> </tt>
<a name="L287"></a><tt class="py-lineno">287</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L288"></a><tt class="py-lineno">288</tt>  <tt class="py-line"><tt class="py-docstring">  We can declare the setter method which is really</tt> </tt>
<a name="L289"></a><tt class="py-lineno">289</tt>  <tt class="py-line"><tt class="py-docstring">  a straightforward extension from the add_function function.::</tt> </tt>
<a name="L290"></a><tt class="py-lineno">290</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L291"></a><tt class="py-lineno">291</tt>  <tt class="py-line"><tt class="py-docstring">    klass.add_method('SetInt', None, [param('int', 'value')])</tt> </tt>
<a name="L292"></a><tt class="py-lineno">292</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L293"></a><tt class="py-lineno">293</tt>  <tt class="py-line"><tt class="py-docstring">  The getter is also pretty straightforward except for the declaration</tt> </tt>
<a name="L294"></a><tt class="py-lineno">294</tt>  <tt class="py-line"><tt class="py-docstring">  of constness:::</tt> </tt>
<a name="L295"></a><tt class="py-lineno">295</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L296"></a><tt class="py-lineno">296</tt>  <tt class="py-line"><tt class="py-docstring">    klass.add_method('GetInt', retval('int'), [], is_const=True)</tt> </tt>
<a name="L297"></a><tt class="py-lineno">297</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L298"></a><tt class="py-lineno">298</tt>  <tt class="py-line"><tt class="py-docstring">  Using this API is also very similar to the struct example we went through</tt> </tt>
<a name="L299"></a><tt class="py-lineno">299</tt>  <tt class="py-line"><tt class="py-docstring">  in the previous section:</tt> </tt>
<a name="L300"></a><tt class="py-lineno">300</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L301"></a><tt class="py-lineno">301</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; my = MyModule.MyClass()</tt> </tt>
<a name="L302"></a><tt class="py-lineno">302</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; my.SetInt(10)</tt> </tt>
<a name="L303"></a><tt class="py-lineno">303</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; v = my.GetInt()</tt> </tt>
<a name="L304"></a><tt class="py-lineno">304</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print v</tt> </tt>
<a name="L305"></a><tt class="py-lineno">305</tt>  <tt class="py-line"><tt class="py-docstring">    10</tt> </tt>
<a name="L306"></a><tt class="py-lineno">306</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L307"></a><tt class="py-lineno">307</tt>  <tt class="py-line"><tt class="py-docstring">  It is also possible to bind inner classes and enums such</tt> </tt>
<a name="L308"></a><tt class="py-lineno">308</tt>  <tt class="py-line"><tt class="py-docstring">  as these:::</tt> </tt>
<a name="L309"></a><tt class="py-lineno">309</tt>  <tt class="py-line"><tt class="py-docstring">    class Outer</tt> </tt>
<a name="L310"></a><tt class="py-lineno">310</tt>  <tt class="py-line"><tt class="py-docstring">    {</tt> </tt>
<a name="L311"></a><tt class="py-lineno">311</tt>  <tt class="py-line"><tt class="py-docstring">    public:</tt> </tt>
<a name="L312"></a><tt class="py-lineno">312</tt>  <tt class="py-line"><tt class="py-docstring">      void Do (void);</tt> </tt>
<a name="L313"></a><tt class="py-lineno">313</tt>  <tt class="py-line"><tt class="py-docstring">      // an inner enum</tt> </tt>
<a name="L314"></a><tt class="py-lineno">314</tt>  <tt class="py-line"><tt class="py-docstring">      enum inner_e</tt> </tt>
<a name="L315"></a><tt class="py-lineno">315</tt>  <tt class="py-line"><tt class="py-docstring">      {</tt> </tt>
<a name="L316"></a><tt class="py-lineno">316</tt>  <tt class="py-line"><tt class="py-docstring">        INNER_A,</tt> </tt>
<a name="L317"></a><tt class="py-lineno">317</tt>  <tt class="py-line"><tt class="py-docstring">        INNER_B,</tt> </tt>
<a name="L318"></a><tt class="py-lineno">318</tt>  <tt class="py-line"><tt class="py-docstring">        INNER_C</tt> </tt>
<a name="L319"></a><tt class="py-lineno">319</tt>  <tt class="py-line"><tt class="py-docstring">      };</tt> </tt>
<a name="L320"></a><tt class="py-lineno">320</tt>  <tt class="py-line"><tt class="py-docstring">      // an inner class</tt> </tt>
<a name="L321"></a><tt class="py-lineno">321</tt>  <tt class="py-line"><tt class="py-docstring">      class Inner</tt> </tt>
<a name="L322"></a><tt class="py-lineno">322</tt>  <tt class="py-line"><tt class="py-docstring">      {</tt> </tt>
<a name="L323"></a><tt class="py-lineno">323</tt>  <tt class="py-line"><tt class="py-docstring">      public:</tt> </tt>
<a name="L324"></a><tt class="py-lineno">324</tt>  <tt class="py-line"><tt class="py-docstring">        void Do (enum Outer::inner_e value);</tt> </tt>
<a name="L325"></a><tt class="py-lineno">325</tt>  <tt class="py-line"><tt class="py-docstring">      };</tt> </tt>
<a name="L326"></a><tt class="py-lineno">326</tt>  <tt class="py-line"><tt class="py-docstring">    };</tt> </tt>
<a name="L327"></a><tt class="py-lineno">327</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L328"></a><tt class="py-lineno">328</tt>  <tt class="py-line"><tt class="py-docstring">  We just need to bind the outer class:::</tt> </tt>
<a name="L329"></a><tt class="py-lineno">329</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L330"></a><tt class="py-lineno">330</tt>  <tt class="py-line"><tt class="py-docstring">    outer = mod.add_class('Outer')</tt> </tt>
<a name="L331"></a><tt class="py-lineno">331</tt>  <tt class="py-line"><tt class="py-docstring">    outer.add_constructor([])</tt> </tt>
<a name="L332"></a><tt class="py-lineno">332</tt>  <tt class="py-line"><tt class="py-docstring">    outer.add_method('Do', None, [])</tt> </tt>
<a name="L333"></a><tt class="py-lineno">333</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L334"></a><tt class="py-lineno">334</tt>  <tt class="py-line"><tt class="py-docstring">  Then, bind its inner enum:::</tt> </tt>
<a name="L335"></a><tt class="py-lineno">335</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L336"></a><tt class="py-lineno">336</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_enum('inner_e', ['INNER_A', 'INNER_B', 'INNER_C'], outer_class=outer)</tt> </tt>
<a name="L337"></a><tt class="py-lineno">337</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L338"></a><tt class="py-lineno">338</tt>  <tt class="py-line"><tt class="py-docstring">  and, finally, bind its inner class:::</tt> </tt>
<a name="L339"></a><tt class="py-lineno">339</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L340"></a><tt class="py-lineno">340</tt>  <tt class="py-line"><tt class="py-docstring">    mod.add_class('Inner', outer_class=outer)</tt> </tt>
<a name="L341"></a><tt class="py-lineno">341</tt>  <tt class="py-line"><tt class="py-docstring">    inner.add_constructor([])</tt> </tt>
<a name="L342"></a><tt class="py-lineno">342</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L343"></a><tt class="py-lineno">343</tt>  <tt class="py-line"><tt class="py-docstring">  The only slightly tricky part is binding the Do method of the Inner</tt> </tt>
<a name="L344"></a><tt class="py-lineno">344</tt>  <tt class="py-line"><tt class="py-docstring">  class since it refers to the enum type defined in the Outer class: we</tt> </tt>
<a name="L345"></a><tt class="py-lineno">345</tt>  <tt class="py-line"><tt class="py-docstring">  simply need to carefully use the fully scoped name of the enum.::</tt> </tt>
<a name="L346"></a><tt class="py-lineno">346</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L347"></a><tt class="py-lineno">347</tt>  <tt class="py-line"><tt class="py-docstring">    inner.add_method('Do', None, [param('Outer::inner_e', value)])</tt> </tt>
<a name="L348"></a><tt class="py-lineno">348</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L349"></a><tt class="py-lineno">349</tt>  <tt class="py-line"><tt class="py-docstring">  The resulting python API reflects the underlying C++ API very closely:</tt> </tt>
<a name="L350"></a><tt class="py-lineno">350</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L351"></a><tt class="py-lineno">351</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L352"></a><tt class="py-lineno">352</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print MyModule.Outer.INNER_A</tt> </tt>
<a name="L353"></a><tt class="py-lineno">353</tt>  <tt class="py-line"><tt class="py-docstring">    0</tt> </tt>
<a name="L354"></a><tt class="py-lineno">354</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; print MyModule.Outer.INNER_B</tt> </tt>
<a name="L355"></a><tt class="py-lineno">355</tt>  <tt class="py-line"><tt class="py-docstring">    1</tt> </tt>
<a name="L356"></a><tt class="py-lineno">356</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; outer = MyModule.Outer()</tt> </tt>
<a name="L357"></a><tt class="py-lineno">357</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; outer.Do()</tt> </tt>
<a name="L358"></a><tt class="py-lineno">358</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; inner = MyModule.Outer.Inner()</tt> </tt>
<a name="L359"></a><tt class="py-lineno">359</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; inner.Do(MyModule.Outer.INNER_A)</tt> </tt>
<a name="L360"></a><tt class="py-lineno">360</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L361"></a><tt class="py-lineno">361</tt>  <tt class="py-line"><tt class="py-docstring">  C++ namespaces</tt> </tt>
<a name="L362"></a><tt class="py-lineno">362</tt>  <tt class="py-line"><tt class="py-docstring">  --------------</tt> </tt>
<a name="L363"></a><tt class="py-lineno">363</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L364"></a><tt class="py-lineno">364</tt>  <tt class="py-line"><tt class="py-docstring">  Wrapping multiple nested namespaces is, of course, possible and represents</tt> </tt>
<a name="L365"></a><tt class="py-lineno">365</tt>  <tt class="py-line"><tt class="py-docstring">  no special challenge. Let's look at an example:::</tt> </tt>
<a name="L366"></a><tt class="py-lineno">366</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L367"></a><tt class="py-lineno">367</tt>  <tt class="py-line"><tt class="py-docstring">    namespace Outer {</tt> </tt>
<a name="L368"></a><tt class="py-lineno">368</tt>  <tt class="py-line"><tt class="py-docstring">      void Do (void);</tt> </tt>
<a name="L369"></a><tt class="py-lineno">369</tt>  <tt class="py-line"><tt class="py-docstring">      class MyClass </tt> </tt>
<a name="L370"></a><tt class="py-lineno">370</tt>  <tt class="py-line"><tt class="py-docstring">      {};</tt> </tt>
<a name="L371"></a><tt class="py-lineno">371</tt>  <tt class="py-line"><tt class="py-docstring">      namespace Inner {</tt> </tt>
<a name="L372"></a><tt class="py-lineno">372</tt>  <tt class="py-line"><tt class="py-docstring">        void Do (void);</tt> </tt>
<a name="L373"></a><tt class="py-lineno">373</tt>  <tt class="py-line"><tt class="py-docstring">        class MyClass </tt> </tt>
<a name="L374"></a><tt class="py-lineno">374</tt>  <tt class="py-line"><tt class="py-docstring">        {};</tt> </tt>
<a name="L375"></a><tt class="py-lineno">375</tt>  <tt class="py-line"><tt class="py-docstring">      } // namespace Inner</tt> </tt>
<a name="L376"></a><tt class="py-lineno">376</tt>  <tt class="py-line"><tt class="py-docstring">    } // namespace Outer</tt> </tt>
<a name="L377"></a><tt class="py-lineno">377</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L378"></a><tt class="py-lineno">378</tt>  <tt class="py-line"><tt class="py-docstring">  First, we need to define the Outer namespace:::</tt> </tt>
<a name="L379"></a><tt class="py-lineno">379</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L380"></a><tt class="py-lineno">380</tt>  <tt class="py-line"><tt class="py-docstring">    mod = Module('MyModule')</tt> </tt>
<a name="L381"></a><tt class="py-lineno">381</tt>  <tt class="py-line"><tt class="py-docstring">    outer = mod.add_cpp_namespace('Outer')</tt> </tt>
<a name="L382"></a><tt class="py-lineno">382</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L383"></a><tt class="py-lineno">383</tt>  <tt class="py-line"><tt class="py-docstring">  Then, register its classes and functions:::</tt> </tt>
<a name="L384"></a><tt class="py-lineno">384</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L385"></a><tt class="py-lineno">385</tt>  <tt class="py-line"><tt class="py-docstring">    outer.add_class('MyClass')</tt> </tt>
<a name="L386"></a><tt class="py-lineno">386</tt>  <tt class="py-line"><tt class="py-docstring">    outer.add_function('Do', None, [])</tt> </tt>
<a name="L387"></a><tt class="py-lineno">387</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L388"></a><tt class="py-lineno">388</tt>  <tt class="py-line"><tt class="py-docstring">  and, finally, define the Inner namespace and its associated</tt> </tt>
<a name="L389"></a><tt class="py-lineno">389</tt>  <tt class="py-line"><tt class="py-docstring">  functions and methods:::</tt> </tt>
<a name="L390"></a><tt class="py-lineno">390</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L391"></a><tt class="py-lineno">391</tt>  <tt class="py-line"><tt class="py-docstring">    inner = outer.add_cpp_namespace('Inner')</tt> </tt>
<a name="L392"></a><tt class="py-lineno">392</tt>  <tt class="py-line"><tt class="py-docstring">    inner.add_class('MyClass')</tt> </tt>
<a name="L393"></a><tt class="py-lineno">393</tt>  <tt class="py-line"><tt class="py-docstring">    inner.add_function('Do', None, [])</tt> </tt>
<a name="L394"></a><tt class="py-lineno">394</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L395"></a><tt class="py-lineno">395</tt>  <tt class="py-line"><tt class="py-docstring">  The resulting API, again, sticks to the underlying C++ API by</tt> </tt>
<a name="L396"></a><tt class="py-lineno">396</tt>  <tt class="py-line"><tt class="py-docstring">  defining one python module for each C++ namespace and making</tt> </tt>
<a name="L397"></a><tt class="py-lineno">397</tt>  <tt class="py-line"><tt class="py-docstring">  sure that the hierarchy of python modules matches the hierarchy</tt> </tt>
<a name="L398"></a><tt class="py-lineno">398</tt>  <tt class="py-line"><tt class="py-docstring">  of C++ namespaces.</tt> </tt>
<a name="L399"></a><tt class="py-lineno">399</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L400"></a><tt class="py-lineno">400</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; import MyModule</tt> </tt>
<a name="L401"></a><tt class="py-lineno">401</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; o = MyModule.Outer.MyClass()</tt> </tt>
<a name="L402"></a><tt class="py-lineno">402</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; i = MyModule.Outer.Inner.MyClass()</tt> </tt>
<a name="L403"></a><tt class="py-lineno">403</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; from MyModule.Outer.Inner import *</tt> </tt>
<a name="L404"></a><tt class="py-lineno">404</tt>  <tt class="py-line"><tt class="py-docstring">    &gt;&gt;&gt; i = MyClass()</tt> </tt>
<a name="L405"></a><tt class="py-lineno">405</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L406"></a><tt class="py-lineno">406</tt>  <tt class="py-line"><tt class="py-docstring">Memory management for pointer types</tt> </tt>
<a name="L407"></a><tt class="py-lineno">407</tt>  <tt class="py-line"><tt class="py-docstring">===================================</tt> </tt>
<a name="L408"></a><tt class="py-lineno">408</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L409"></a><tt class="py-lineno">409</tt>  <tt class="py-line"><tt class="py-docstring">  Until then, we have shown how to pass back and forth data through C/C++ APIs</tt> </tt>
<a name="L410"></a><tt class="py-lineno">410</tt>  <tt class="py-line"><tt class="py-docstring">  only by value but, a large fraction of real-world APIs use raw pointers</tt> </tt>
<a name="L411"></a><tt class="py-lineno">411</tt>  <tt class="py-line"><tt class="py-docstring">  (and, in the case of C++, smart pointers) as arguments or return values </tt> </tt>
<a name="L412"></a><tt class="py-lineno">412</tt>  <tt class="py-line"><tt class="py-docstring">  of functions/methods.</tt> </tt>
<a name="L413"></a><tt class="py-lineno">413</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L414"></a><tt class="py-lineno">414</tt>  <tt class="py-line"><tt class="py-docstring">  Rather than try to explain the detail of every option offered by pybindgen</tt> </tt>
<a name="L415"></a><tt class="py-lineno">415</tt>  <tt class="py-line"><tt class="py-docstring">  to deal with pointers, we will go through a couple of very classic memory</tt> </tt>
<a name="L416"></a><tt class="py-lineno">416</tt>  <tt class="py-line"><tt class="py-docstring">  management schemes and examples.</tt> </tt>
<a name="L417"></a><tt class="py-lineno">417</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L418"></a><tt class="py-lineno">418</tt>  <tt class="py-line"><tt class="py-docstring">  Function returns pointer</tt> </tt>
<a name="L419"></a><tt class="py-lineno">419</tt>  <tt class="py-line"><tt class="py-docstring">  ------------------------</tt> </tt>
<a name="L420"></a><tt class="py-lineno">420</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L421"></a><tt class="py-lineno">421</tt>  <tt class="py-line"><tt class="py-docstring">    The API to bind::</tt> </tt>
<a name="L422"></a><tt class="py-lineno">422</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L423"></a><tt class="py-lineno">423</tt>  <tt class="py-line"><tt class="py-docstring">      class MyClass;</tt> </tt>
<a name="L424"></a><tt class="py-lineno">424</tt>  <tt class="py-line"><tt class="py-docstring">      MyClass *DoSomethingAndReturnClass (void);</tt> </tt>
<a name="L425"></a><tt class="py-lineno">425</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L426"></a><tt class="py-lineno">426</tt>  <tt class="py-line"><tt class="py-docstring">    First, we declare the MyClass type::</tt> </tt>
<a name="L427"></a><tt class="py-lineno">427</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L428"></a><tt class="py-lineno">428</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_class('MyClass')</tt> </tt>
<a name="L429"></a><tt class="py-lineno">429</tt>  <tt class="py-line"><tt class="py-docstring">      ...</tt> </tt>
<a name="L430"></a><tt class="py-lineno">430</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L431"></a><tt class="py-lineno">431</tt>  <tt class="py-line"><tt class="py-docstring">    Then, if we assume that the function returns ownership of the pointer to the caller, we</tt> </tt>
<a name="L432"></a><tt class="py-lineno">432</tt>  <tt class="py-line"><tt class="py-docstring">    can write::</tt> </tt>
<a name="L433"></a><tt class="py-lineno">433</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L434"></a><tt class="py-lineno">434</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoSomethingAndReturnClass', retval('MyClass *', caller_owns_return=True), [])</tt> </tt>
<a name="L435"></a><tt class="py-lineno">435</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L436"></a><tt class="py-lineno">436</tt>  <tt class="py-line"><tt class="py-docstring">    The above will tell pybindgen that the caller (the python runtime) becomes</tt> </tt>
<a name="L437"></a><tt class="py-lineno">437</tt>  <tt class="py-line"><tt class="py-docstring">    responsible for deleting the instance of MyClass returned by the function</tt> </tt>
<a name="L438"></a><tt class="py-lineno">438</tt>  <tt class="py-line"><tt class="py-docstring">    DoSomethingAndReturnClass when it is done with it.</tt> </tt>
<a name="L439"></a><tt class="py-lineno">439</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L440"></a><tt class="py-lineno">440</tt>  <tt class="py-line"><tt class="py-docstring">    Of course, it is possible to not give back ownership of the returned pointer</tt> </tt>
<a name="L441"></a><tt class="py-lineno">441</tt>  <tt class="py-line"><tt class="py-docstring">    to the caller::</tt> </tt>
<a name="L442"></a><tt class="py-lineno">442</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L443"></a><tt class="py-lineno">443</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoSomethingAndReturnClass', retval('MyClass *', caller_owns_return=False), [])</tt> </tt>
<a name="L444"></a><tt class="py-lineno">444</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L445"></a><tt class="py-lineno">445</tt>  <tt class="py-line"><tt class="py-docstring">    Which would make the python runtime assume that the lifetime of the returned pointer</tt> </tt>
<a name="L446"></a><tt class="py-lineno">446</tt>  <tt class="py-line"><tt class="py-docstring">    is longer than the associated python object.</tt> </tt>
<a name="L447"></a><tt class="py-lineno">447</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L448"></a><tt class="py-lineno">448</tt>  <tt class="py-line"><tt class="py-docstring">  Function takes pointer</tt> </tt>
<a name="L449"></a><tt class="py-lineno">449</tt>  <tt class="py-line"><tt class="py-docstring">  ----------------------</tt> </tt>
<a name="L450"></a><tt class="py-lineno">450</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L451"></a><tt class="py-lineno">451</tt>  <tt class="py-line"><tt class="py-docstring">    The API to bind::</tt> </tt>
<a name="L452"></a><tt class="py-lineno">452</tt>  <tt class="py-line"><tt class="py-docstring">  </tt> </tt>
<a name="L453"></a><tt class="py-lineno">453</tt>  <tt class="py-line"><tt class="py-docstring">      class MyClass;</tt> </tt>
<a name="L454"></a><tt class="py-lineno">454</tt>  <tt class="py-line"><tt class="py-docstring">      void DoWithClass (MyClass *cls);</tt> </tt>
<a name="L455"></a><tt class="py-lineno">455</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L456"></a><tt class="py-lineno">456</tt>  <tt class="py-line"><tt class="py-docstring">    If we assume that the callee takes ownership of the input pointer, we can write::</tt> </tt>
<a name="L457"></a><tt class="py-lineno">457</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L458"></a><tt class="py-lineno">458</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoWithClass', None, [param('MyClass *', 'cls', transfer_ownership = True)])</tt> </tt>
<a name="L459"></a><tt class="py-lineno">459</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L460"></a><tt class="py-lineno">460</tt>  <tt class="py-line"><tt class="py-docstring">    Which will make python keep a handle on the MyClass instance but never destroy it himself</tt> </tt>
<a name="L461"></a><tt class="py-lineno">461</tt>  <tt class="py-line"><tt class="py-docstring">    and rely on the callee to destroy it at the right time. This kind of scheme is obviously</tt> </tt>
<a name="L462"></a><tt class="py-lineno">462</tt>  <tt class="py-line"><tt class="py-docstring">    a bit dangerous because python has no way of knowing when the underlying MyClass instance</tt> </tt>
<a name="L463"></a><tt class="py-lineno">463</tt>  <tt class="py-line"><tt class="py-docstring">    is really destroyed so, if you try to invoke methods on it _after_ it has been destroyed,</tt> </tt>
<a name="L464"></a><tt class="py-lineno">464</tt>  <tt class="py-line"><tt class="py-docstring">    bad things will obviously happen.</tt> </tt>
<a name="L465"></a><tt class="py-lineno">465</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L466"></a><tt class="py-lineno">466</tt>  <tt class="py-line"><tt class="py-docstring">    If, instead, we assume that the caller keeps ownership of the pointer, we can write</tt> </tt>
<a name="L467"></a><tt class="py-lineno">467</tt>  <tt class="py-line"><tt class="py-docstring">    the much safer version::</tt> </tt>
<a name="L468"></a><tt class="py-lineno">468</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L469"></a><tt class="py-lineno">469</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoWithClass', None, [param('MyClass *', 'cls', transfer_ownership = False)])</tt> </tt>
<a name="L470"></a><tt class="py-lineno">470</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L471"></a><tt class="py-lineno">471</tt>  <tt class="py-line"><tt class="py-docstring">    Which will allow python to delete the MyClass instance only when the associated python wrapper</tt> </tt>
<a name="L472"></a><tt class="py-lineno">472</tt>  <tt class="py-line"><tt class="py-docstring">    disappears.</tt> </tt>
<a name="L473"></a><tt class="py-lineno">473</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L474"></a><tt class="py-lineno">474</tt>  <tt class="py-line"><tt class="py-docstring">  A reference-counted object</tt> </tt>
<a name="L475"></a><tt class="py-lineno">475</tt>  <tt class="py-line"><tt class="py-docstring">  --------------------------</tt> </tt>
<a name="L476"></a><tt class="py-lineno">476</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L477"></a><tt class="py-lineno">477</tt>  <tt class="py-line"><tt class="py-docstring">    A nice way to avoid some of the ambiguities of the above-mentioned API bindings is to </tt> </tt>
<a name="L478"></a><tt class="py-lineno">478</tt>  <tt class="py-line"><tt class="py-docstring">    use reference-counted C or C++ objects which must provide a pair of functions or methods</tt> </tt>
<a name="L479"></a><tt class="py-lineno">479</tt>  <tt class="py-line"><tt class="py-docstring">    to increase or decrease the reference count of the object. For example, a classic</tt> </tt>
<a name="L480"></a><tt class="py-lineno">480</tt>  <tt class="py-line"><tt class="py-docstring">    C++ reference-counted class::</tt> </tt>
<a name="L481"></a><tt class="py-lineno">481</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L482"></a><tt class="py-lineno">482</tt>  <tt class="py-line"><tt class="py-docstring">      class MyClass </tt> </tt>
<a name="L483"></a><tt class="py-lineno">483</tt>  <tt class="py-line"><tt class="py-docstring">      {</tt> </tt>
<a name="L484"></a><tt class="py-lineno">484</tt>  <tt class="py-line"><tt class="py-docstring">      public:</tt> </tt>
<a name="L485"></a><tt class="py-lineno">485</tt>  <tt class="py-line"><tt class="py-docstring">        void Ref (void);</tt> </tt>
<a name="L486"></a><tt class="py-lineno">486</tt>  <tt class="py-line"><tt class="py-docstring">        void Unref (void);</tt> </tt>
<a name="L487"></a><tt class="py-lineno">487</tt>  <tt class="py-line"><tt class="py-docstring">        uint32_t PeekRef (void);</tt> </tt>
<a name="L488"></a><tt class="py-lineno">488</tt>  <tt class="py-line"><tt class="py-docstring">      };</tt> </tt>
<a name="L489"></a><tt class="py-lineno">489</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L490"></a><tt class="py-lineno">490</tt>  <tt class="py-line"><tt class="py-docstring">    And the associated function which takes a pointer::</tt> </tt>
<a name="L491"></a><tt class="py-lineno">491</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L492"></a><tt class="py-lineno">492</tt>  <tt class="py-line"><tt class="py-docstring">      void DoSomething (MyClass *cls);</tt> </tt>
<a name="L493"></a><tt class="py-lineno">493</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L494"></a><tt class="py-lineno">494</tt>  <tt class="py-line"><tt class="py-docstring">    To wrap this class, we first need to declare our class::</tt> </tt>
<a name="L495"></a><tt class="py-lineno">495</tt>  <tt class="py-line"><tt class="py-docstring">      from pybindgen import cppclass</tt> </tt>
<a name="L496"></a><tt class="py-lineno">496</tt>  <tt class="py-line"><tt class="py-docstring">      [...]</tt> </tt>
<a name="L497"></a><tt class="py-lineno">497</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_class('MyClass', memory_policy=cppclass.ReferenceCountingMethodsPolicy( </tt> </tt>
<a name="L498"></a><tt class="py-lineno">498</tt>  <tt class="py-line"><tt class="py-docstring">                        incref_method='Ref', </tt> </tt>
<a name="L499"></a><tt class="py-lineno">499</tt>  <tt class="py-line"><tt class="py-docstring">                        decref_method='Unref', </tt> </tt>
<a name="L500"></a><tt class="py-lineno">500</tt>  <tt class="py-line"><tt class="py-docstring">                        peekref_method='PeekRef'))</tt> </tt>
<a name="L501"></a><tt class="py-lineno">501</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L502"></a><tt class="py-lineno">502</tt>  <tt class="py-line"><tt class="py-docstring">    The above allows pybindgen to maintain and track the reference count</tt> </tt>
<a name="L503"></a><tt class="py-lineno">503</tt>  <tt class="py-line"><tt class="py-docstring">    of the MyClass object while the code below shows how we can declare</tt> </tt>
<a name="L504"></a><tt class="py-lineno">504</tt>  <tt class="py-line"><tt class="py-docstring">    a function taking a pointer as input::</tt> </tt>
<a name="L505"></a><tt class="py-lineno">505</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L506"></a><tt class="py-lineno">506</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoSomething', None, [param('MyClass *', 'cls', transfer_ownership=False)]</tt> </tt>
<a name="L507"></a><tt class="py-lineno">507</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L508"></a><tt class="py-lineno">508</tt>  <tt class="py-line"><tt class="py-docstring">    Here, the meaning of transfer_ownership changes slightly.</tt> </tt>
<a name="L509"></a><tt class="py-lineno">509</tt>  <tt class="py-line"><tt class="py-docstring">    Whithout reference counting, transfer_ownership refers to the</tt> </tt>
<a name="L510"></a><tt class="py-lineno">510</tt>  <tt class="py-line"><tt class="py-docstring">    transfer of the object as a whole, i.e. either the caller or</tt> </tt>
<a name="L511"></a><tt class="py-lineno">511</tt>  <tt class="py-line"><tt class="py-docstring">    callee will own the object in the end, but not both.  With</tt> </tt>
<a name="L512"></a><tt class="py-lineno">512</tt>  <tt class="py-line"><tt class="py-docstring">    reference counting, transfer_ownership refers to the transfer of a</tt> </tt>
<a name="L513"></a><tt class="py-lineno">513</tt>  <tt class="py-line"><tt class="py-docstring">    _reference_.  In this example, transfer_ownership=False means that</tt> </tt>
<a name="L514"></a><tt class="py-lineno">514</tt>  <tt class="py-line"><tt class="py-docstring">    the caller will not "steal" our reference, i.e. it will either not</tt> </tt>
<a name="L515"></a><tt class="py-lineno">515</tt>  <tt class="py-line"><tt class="py-docstring">    keep a reference to our object for itself, or if it does it</tt> </tt>
<a name="L516"></a><tt class="py-lineno">516</tt>  <tt class="py-line"><tt class="py-docstring">    creates its own reference to the object by calling the incref</tt> </tt>
<a name="L517"></a><tt class="py-lineno">517</tt>  <tt class="py-line"><tt class="py-docstring">    method.  If transfer_ownership=True it would mean that the caller</tt> </tt>
<a name="L518"></a><tt class="py-lineno">518</tt>  <tt class="py-line"><tt class="py-docstring">    would keep the passed in reference to itself, and if the caller</tt> </tt>
<a name="L519"></a><tt class="py-lineno">519</tt>  <tt class="py-line"><tt class="py-docstring">    wants to keep the reference it must call the incref method first.</tt> </tt>
<a name="L520"></a><tt class="py-lineno">520</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L521"></a><tt class="py-lineno">521</tt>  <tt class="py-line"><tt class="py-docstring">    A more interesting case is that of returning such a reference counted </tt> </tt>
<a name="L522"></a><tt class="py-lineno">522</tt>  <tt class="py-line"><tt class="py-docstring">    object from a function::</tt> </tt>
<a name="L523"></a><tt class="py-lineno">523</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L524"></a><tt class="py-lineno">524</tt>  <tt class="py-line"><tt class="py-docstring">      MyClass *DoSomething (void);</tt> </tt>
<a name="L525"></a><tt class="py-lineno">525</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L526"></a><tt class="py-lineno">526</tt>  <tt class="py-line"><tt class="py-docstring">    While classic reference counting rules require that the callee returns</tt> </tt>
<a name="L527"></a><tt class="py-lineno">527</tt>  <tt class="py-line"><tt class="py-docstring">    a reference to the caller (i.e., it calls Ref on behalf of the caller</tt> </tt>
<a name="L528"></a><tt class="py-lineno">528</tt>  <tt class="py-line"><tt class="py-docstring">    before returning the pointer), some APIs will undoubtedly return a pointer</tt> </tt>
<a name="L529"></a><tt class="py-lineno">529</tt>  <tt class="py-line"><tt class="py-docstring">    and expect the caller to acquire a reference to the returned object by</tt> </tt>
<a name="L530"></a><tt class="py-lineno">530</tt>  <tt class="py-line"><tt class="py-docstring">    calling Ref himself. Pybindgen hopefully can be made to support this</tt> </tt>
<a name="L531"></a><tt class="py-lineno">531</tt>  <tt class="py-line"><tt class="py-docstring">    case too::</tt> </tt>
<a name="L532"></a><tt class="py-lineno">532</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L533"></a><tt class="py-lineno">533</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoSomething', retval('MyClass *', caller_owns_return=False), [])</tt> </tt>
<a name="L534"></a><tt class="py-lineno">534</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L535"></a><tt class="py-lineno">535</tt>  <tt class="py-line"><tt class="py-docstring">    Which instructs pybindgen that DoSomething is not to be trusted and that it should</tt> </tt>
<a name="L536"></a><tt class="py-lineno">536</tt>  <tt class="py-line"><tt class="py-docstring">    acquire ownership of the returned pointer if it needs to keep track of it.</tt> </tt>
<a name="L537"></a><tt class="py-lineno">537</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L538"></a><tt class="py-lineno">538</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L539"></a><tt class="py-lineno">539</tt>  <tt class="py-line"><tt class="py-docstring">  A STL container</tt> </tt>
<a name="L540"></a><tt class="py-lineno">540</tt>  <tt class="py-line"><tt class="py-docstring">  ---------------</tt> </tt>
<a name="L541"></a><tt class="py-lineno">541</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L542"></a><tt class="py-lineno">542</tt>  <tt class="py-line"><tt class="py-docstring">    If you have a function that takes a STL container, you have to</tt> </tt>
<a name="L543"></a><tt class="py-lineno">543</tt>  <tt class="py-line"><tt class="py-docstring">    tell pybindgen to wrap the container first::</tt> </tt>
<a name="L544"></a><tt class="py-lineno">544</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L545"></a><tt class="py-lineno">545</tt>  <tt class="py-line"><tt class="py-docstring">      void DoSomething (std::list&lt;std::string&gt; const &amp;listOfStrings);</tt> </tt>
<a name="L546"></a><tt class="py-lineno">546</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L547"></a><tt class="py-lineno">547</tt>  <tt class="py-line"><tt class="py-docstring">    Is wrapped by::</tt> </tt>
<a name="L548"></a><tt class="py-lineno">548</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L549"></a><tt class="py-lineno">549</tt>  <tt class="py-line"><tt class="py-docstring">      module.add_container('std::list&lt;std::string&gt;', 'std::string', 'list') # declare a container only once</tt> </tt>
<a name="L550"></a><tt class="py-lineno">550</tt>  <tt class="py-line"><tt class="py-docstring">      [...]</tt> </tt>
<a name="L551"></a><tt class="py-lineno">551</tt>  <tt class="py-line"><tt class="py-docstring">      mod.add_function('DoSomething', None, [param('std::list&lt;std::string&gt; const &amp;', 'listOfStrings')])</tt> </tt>
<a name="L552"></a><tt class="py-lineno">552</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L553"></a><tt class="py-lineno">553</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L554"></a><tt class="py-lineno">554</tt>  <tt class="py-line"><tt class="py-docstring">Subclassing a C++ class from python</tt> </tt>
<a name="L555"></a><tt class="py-lineno">555</tt>  <tt class="py-line"><tt class="py-docstring">===================================</tt> </tt>
<a name="L556"></a><tt class="py-lineno">556</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L557"></a><tt class="py-lineno">557</tt>  <tt class="py-line"><tt class="py-docstring">Extending a C++ class or namespace from python</tt> </tt>
<a name="L558"></a><tt class="py-lineno">558</tt>  <tt class="py-line"><tt class="py-docstring">==============================================</tt> </tt>
<a name="L559"></a><tt class="py-lineno">559</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L560"></a><tt class="py-lineno">560</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L561"></a><tt class="py-lineno">561</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L562"></a><tt class="py-lineno">562</tt>  <tt class="py-line"><tt class="py-docstring">Basic Interface with Error Handling</tt> </tt>
<a name="L563"></a><tt class="py-lineno">563</tt>  <tt class="py-line"><tt class="py-docstring">===================================</tt> </tt>
<a name="L564"></a><tt class="py-lineno">564</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L565"></a><tt class="py-lineno">565</tt>  <tt class="py-line"><tt class="py-docstring">  It is also possible to declare a error handler.  The error handler</tt> </tt>
<a name="L566"></a><tt class="py-lineno">566</tt>  <tt class="py-line"><tt class="py-docstring">  will be invoked for API definitions that cannot be wrapped for some</tt> </tt>
<a name="L567"></a><tt class="py-lineno">567</tt>  <tt class="py-line"><tt class="py-docstring">  reason::</tt> </tt>
<a name="L568"></a><tt class="py-lineno">568</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L569"></a><tt class="py-lineno">569</tt>  <tt class="py-line"><tt class="py-docstring">    #! /usr/bin/env python</tt> </tt>
<a name="L570"></a><tt class="py-lineno">570</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L571"></a><tt class="py-lineno">571</tt>  <tt class="py-line"><tt class="py-docstring">    import sys</tt> </tt>
<a name="L572"></a><tt class="py-lineno">572</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L573"></a><tt class="py-lineno">573</tt>  <tt class="py-line"><tt class="py-docstring">    import pybindgen</tt> </tt>
<a name="L574"></a><tt class="py-lineno">574</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import Module, FileCodeSink, retval, param</tt> </tt>
<a name="L575"></a><tt class="py-lineno">575</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L576"></a><tt class="py-lineno">576</tt>  <tt class="py-line"><tt class="py-docstring">    import pybindgen.settings</tt> </tt>
<a name="L577"></a><tt class="py-lineno">577</tt>  <tt class="py-line"><tt class="py-docstring">    import warnings</tt> </tt>
<a name="L578"></a><tt class="py-lineno">578</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L579"></a><tt class="py-lineno">579</tt>  <tt class="py-line"><tt class="py-docstring">    class ErrorHandler(pybindgen.settings.ErrorHandler):</tt> </tt>
<a name="L580"></a><tt class="py-lineno">580</tt>  <tt class="py-line"><tt class="py-docstring">        def handle_error(self, wrapper, exception, traceback_):</tt> </tt>
<a name="L581"></a><tt class="py-lineno">581</tt>  <tt class="py-line"><tt class="py-docstring">            warnings.warn("exception %r in wrapper %s" % (exception, wrapper))</tt> </tt>
<a name="L582"></a><tt class="py-lineno">582</tt>  <tt class="py-line"><tt class="py-docstring">            return True</tt> </tt>
<a name="L583"></a><tt class="py-lineno">583</tt>  <tt class="py-line"><tt class="py-docstring">    pybindgen.settings.error_handler = ErrorHandler()</tt> </tt>
<a name="L584"></a><tt class="py-lineno">584</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L585"></a><tt class="py-lineno">585</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L586"></a><tt class="py-lineno">586</tt>  <tt class="py-line"><tt class="py-docstring">    def my_module_gen(out_file):</tt> </tt>
<a name="L587"></a><tt class="py-lineno">587</tt>  <tt class="py-line"><tt class="py-docstring">        pybindgen.write_preamble(FileCodeSink(out_file))</tt> </tt>
<a name="L588"></a><tt class="py-lineno">588</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L589"></a><tt class="py-lineno">589</tt>  <tt class="py-line"><tt class="py-docstring">        mod = Module('a')</tt> </tt>
<a name="L590"></a><tt class="py-lineno">590</tt>  <tt class="py-line"><tt class="py-docstring">        mod.add_include('"a.h"')</tt> </tt>
<a name="L591"></a><tt class="py-lineno">591</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L592"></a><tt class="py-lineno">592</tt>  <tt class="py-line"><tt class="py-docstring">        mod.add_function('ADoA', None, [])</tt> </tt>
<a name="L593"></a><tt class="py-lineno">593</tt>  <tt class="py-line"><tt class="py-docstring">        mod.add_function('ADoB', None, [param('uint32_t', 'b')])</tt> </tt>
<a name="L594"></a><tt class="py-lineno">594</tt>  <tt class="py-line"><tt class="py-docstring">        mod.add_function('ADoC', retval('uint32_t'), [])</tt> </tt>
<a name="L595"></a><tt class="py-lineno">595</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L596"></a><tt class="py-lineno">596</tt>  <tt class="py-line"><tt class="py-docstring">        mod.generate(FileCodeSink(out_file) )</tt> </tt>
<a name="L597"></a><tt class="py-lineno">597</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L598"></a><tt class="py-lineno">598</tt>  <tt class="py-line"><tt class="py-docstring">    if __name__ == '__main__':</tt> </tt>
<a name="L599"></a><tt class="py-lineno">599</tt>  <tt class="py-line"><tt class="py-docstring">        my_module_gen(sys.stdout)</tt> </tt>
<a name="L600"></a><tt class="py-lineno">600</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L601"></a><tt class="py-lineno">601</tt>  <tt class="py-line"><tt class="py-docstring">  In this example, we register a error handler that allows PyBindGen</tt> </tt>
<a name="L602"></a><tt class="py-lineno">602</tt>  <tt class="py-line"><tt class="py-docstring">  to simply ignore API definitions with errors, and not wrap them, but</tt> </tt>
<a name="L603"></a><tt class="py-lineno">603</tt>  <tt class="py-line"><tt class="py-docstring">  move on.</tt> </tt>
<a name="L604"></a><tt class="py-lineno">604</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L605"></a><tt class="py-lineno">605</tt>  <tt class="py-line"><tt class="py-docstring">  The difference between is Parameter.new(...) and param(...), as well</tt> </tt>
<a name="L606"></a><tt class="py-lineno">606</tt>  <tt class="py-line"><tt class="py-docstring">  as between ReturnValue.new(...) and retval(...) is to be noted here.</tt> </tt>
<a name="L607"></a><tt class="py-lineno">607</tt>  <tt class="py-line"><tt class="py-docstring">  The main difference is not that param(...) and retval(...) are</tt> </tt>
<a name="L608"></a><tt class="py-lineno">608</tt>  <tt class="py-line"><tt class="py-docstring">  shorter, it is that they allow delayed error handling.  For example,</tt> </tt>
<a name="L609"></a><tt class="py-lineno">609</tt>  <tt class="py-line"><tt class="py-docstring">  when you put Parameter.new("type that does not exist", "foo") in</tt> </tt>
<a name="L610"></a><tt class="py-lineno">610</tt>  <tt class="py-line"><tt class="py-docstring">  your python script, a TypeLookupError exception is raised and it is</tt> </tt>
<a name="L611"></a><tt class="py-lineno">611</tt>  <tt class="py-line"><tt class="py-docstring">  not possible for the error handler to catch it.  However, param(...)</tt> </tt>
<a name="L612"></a><tt class="py-lineno">612</tt>  <tt class="py-line"><tt class="py-docstring">  does not try to lookup the type handler immediately and instead lets</tt> </tt>
<a name="L613"></a><tt class="py-lineno">613</tt>  <tt class="py-line"><tt class="py-docstring">  Module.add_function() do that in a way that the error handler can be</tt> </tt>
<a name="L614"></a><tt class="py-lineno">614</tt>  <tt class="py-line"><tt class="py-docstring">  invoked and the function is simply not wrapped if the error handler</tt> </tt>
<a name="L615"></a><tt class="py-lineno">615</tt>  <tt class="py-line"><tt class="py-docstring">  says so.</tt> </tt>
<a name="L616"></a><tt class="py-lineno">616</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L617"></a><tt class="py-lineno">617</tt>  <tt class="py-line"><tt class="py-docstring">  Header file scanning with (py)gccxml</tt> </tt>
<a name="L618"></a><tt class="py-lineno">618</tt>  <tt class="py-line"><tt class="py-docstring">  ------------------------------------</tt> </tt>
<a name="L619"></a><tt class="py-lineno">619</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L620"></a><tt class="py-lineno">620</tt>  <tt class="py-line"><tt class="py-docstring">  If you have gccxml and pygccxml installed, PyBindGen can use them to</tt> </tt>
<a name="L621"></a><tt class="py-lineno">621</tt>  <tt class="py-line"><tt class="py-docstring">  scan the API definitions directly from the header files::</tt> </tt>
<a name="L622"></a><tt class="py-lineno">622</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L623"></a><tt class="py-lineno">623</tt>  <tt class="py-line"><tt class="py-docstring">    #! /usr/bin/env python</tt> </tt>
<a name="L624"></a><tt class="py-lineno">624</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L625"></a><tt class="py-lineno">625</tt>  <tt class="py-line"><tt class="py-docstring">    import sys</tt> </tt>
<a name="L626"></a><tt class="py-lineno">626</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L627"></a><tt class="py-lineno">627</tt>  <tt class="py-line"><tt class="py-docstring">    import pybindgen</tt> </tt>
<a name="L628"></a><tt class="py-lineno">628</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import FileCodeSink</tt> </tt>
<a name="L629"></a><tt class="py-lineno">629</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen.gccxmlparser import ModuleParser</tt> </tt>
<a name="L630"></a><tt class="py-lineno">630</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L631"></a><tt class="py-lineno">631</tt>  <tt class="py-line"><tt class="py-docstring">    def my_module_gen():</tt> </tt>
<a name="L632"></a><tt class="py-lineno">632</tt>  <tt class="py-line"><tt class="py-docstring">        module_parser = ModuleParser('a1', '::')</tt> </tt>
<a name="L633"></a><tt class="py-lineno">633</tt>  <tt class="py-line"><tt class="py-docstring">        module = module_parser.parse([sys.argv[1]])</tt> </tt>
<a name="L634"></a><tt class="py-lineno">634</tt>  <tt class="py-line"><tt class="py-docstring">        module.add_include('"a.h"')</tt> </tt>
<a name="L635"></a><tt class="py-lineno">635</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L636"></a><tt class="py-lineno">636</tt>  <tt class="py-line"><tt class="py-docstring">        pybindgen.write_preamble(FileCodeSink(sys.stdout))</tt> </tt>
<a name="L637"></a><tt class="py-lineno">637</tt>  <tt class="py-line"><tt class="py-docstring">        module.generate(FileCodeSink(sys.stdout))</tt> </tt>
<a name="L638"></a><tt class="py-lineno">638</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L639"></a><tt class="py-lineno">639</tt>  <tt class="py-line"><tt class="py-docstring">    if __name__ == '__main__':</tt> </tt>
<a name="L640"></a><tt class="py-lineno">640</tt>  <tt class="py-line"><tt class="py-docstring">        my_module_gen()</tt> </tt>
<a name="L641"></a><tt class="py-lineno">641</tt>  <tt class="py-line"><tt class="py-docstring">  </tt> </tt>
<a name="L642"></a><tt class="py-lineno">642</tt>  <tt class="py-line"><tt class="py-docstring">  The above script will generate the bindings for the module directly.</tt> </tt>
<a name="L643"></a><tt class="py-lineno">643</tt>  <tt class="py-line"><tt class="py-docstring">  It expects the input header file, a.h, as first command line</tt> </tt>
<a name="L644"></a><tt class="py-lineno">644</tt>  <tt class="py-line"><tt class="py-docstring">  argument.</tt> </tt>
<a name="L645"></a><tt class="py-lineno">645</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L646"></a><tt class="py-lineno">646</tt>  <tt class="py-line"><tt class="py-docstring">  Header file scanning with (py)gccxml: python intermediate file</tt> </tt>
<a name="L647"></a><tt class="py-lineno">647</tt>  <tt class="py-line"><tt class="py-docstring">  --------------------------------------------------------------</tt> </tt>
<a name="L648"></a><tt class="py-lineno">648</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L649"></a><tt class="py-lineno">649</tt>  <tt class="py-line"><tt class="py-docstring">  The final code generation flow supported by PyBindGen is a hybrid of</tt> </tt>
<a name="L650"></a><tt class="py-lineno">650</tt>  <tt class="py-line"><tt class="py-docstring">  the previous ones.  One script scans C/C++ header files, but instead</tt> </tt>
<a name="L651"></a><tt class="py-lineno">651</tt>  <tt class="py-line"><tt class="py-docstring">  of generating C/C++ binding code directly it instead generates a</tt> </tt>
<a name="L652"></a><tt class="py-lineno">652</tt>  <tt class="py-line"><tt class="py-docstring">  PyBindGen based Python script::</tt> </tt>
<a name="L653"></a><tt class="py-lineno">653</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L654"></a><tt class="py-lineno">654</tt>  <tt class="py-line"><tt class="py-docstring">    #! /usr/bin/env python</tt> </tt>
<a name="L655"></a><tt class="py-lineno">655</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L656"></a><tt class="py-lineno">656</tt>  <tt class="py-line"><tt class="py-docstring">    import sys</tt> </tt>
<a name="L657"></a><tt class="py-lineno">657</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L658"></a><tt class="py-lineno">658</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen import FileCodeSink</tt> </tt>
<a name="L659"></a><tt class="py-lineno">659</tt>  <tt class="py-line"><tt class="py-docstring">    from pybindgen.gccxmlparser import ModuleParser</tt> </tt>
<a name="L660"></a><tt class="py-lineno">660</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L661"></a><tt class="py-lineno">661</tt>  <tt class="py-line"><tt class="py-docstring">    def my_module_gen():</tt> </tt>
<a name="L662"></a><tt class="py-lineno">662</tt>  <tt class="py-line"><tt class="py-docstring">        module_parser = ModuleParser('a2', '::')</tt> </tt>
<a name="L663"></a><tt class="py-lineno">663</tt>  <tt class="py-line"><tt class="py-docstring">        module_parser.parse([sys.argv[1]], includes=['"a.h"'], pygen_sink=FileCodeSink(sys.stdout))</tt> </tt>
<a name="L664"></a><tt class="py-lineno">664</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L665"></a><tt class="py-lineno">665</tt>  <tt class="py-line"><tt class="py-docstring">    if __name__ == '__main__':</tt> </tt>
<a name="L666"></a><tt class="py-lineno">666</tt>  <tt class="py-line"><tt class="py-docstring">        my_module_gen()</tt> </tt>
<a name="L667"></a><tt class="py-lineno">667</tt>  <tt class="py-line"><tt class="py-docstring"> </tt> </tt>
<a name="L668"></a><tt class="py-lineno">668</tt>  <tt class="py-line"><tt class="py-docstring">  The above script produces a Python program on stdout.  Running the</tt> </tt>
<a name="L669"></a><tt class="py-lineno">669</tt>  <tt class="py-line"><tt class="py-docstring">  generated Python program will, in turn, generate the C++ code</tt> </tt>
<a name="L670"></a><tt class="py-lineno">670</tt>  <tt class="py-line"><tt class="py-docstring">  binding our interface.</tt> </tt>
<a name="L671"></a><tt class="py-lineno">671</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L672"></a><tt class="py-lineno">672</tt>  <tt class="py-line"><tt class="py-docstring">"""</tt> </tt>
<a name="L673"></a><tt class="py-lineno">673</tt>  <tt class="py-line"> </tt>
<a name="L674"></a><tt class="py-lineno">674</tt>  <tt class="py-line"> </tt>
<a name="L675"></a><tt class="py-lineno">675</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-0" class="py-name" targets="Package pybindgen.typehandlers=pybindgen.typehandlers-module.html"><a title="pybindgen.typehandlers" class="py-name" href="#" onclick="return doclink('link-0', 'typehandlers', 'link-0');">typehandlers</a></tt><tt class="py-op">.</tt><tt id="link-1" class="py-name" targets="Module pybindgen.typehandlers.base=pybindgen.typehandlers.base-module.html"><a title="pybindgen.typehandlers.base" class="py-name" href="#" onclick="return doclink('link-1', 'base', 'link-1');">base</a></tt> <tt class="py-keyword">import</tt> <tt id="link-2" class="py-name" targets="Class pybindgen.typehandlers.base.ReturnValue=pybindgen.typehandlers.base.ReturnValue-class.html"><a title="pybindgen.typehandlers.base.ReturnValue" class="py-name" href="#" onclick="return doclink('link-2', 'ReturnValue', 'link-2');">ReturnValue</a></tt><tt class="py-op">,</tt> <tt id="link-3" class="py-name" targets="Class pybindgen.typehandlers.base.Parameter=pybindgen.typehandlers.base.Parameter-class.html"><a title="pybindgen.typehandlers.base.Parameter" class="py-name" href="#" onclick="return doclink('link-3', 'Parameter', 'link-3');">Parameter</a></tt> </tt>
<a name="L676"></a><tt class="py-lineno">676</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-4" class="py-name" targets="Variable pybindgen.container.Container.module=pybindgen.container.Container-class.html#module,Variable pybindgen.cppclass.CppClass.module=pybindgen.cppclass.CppClass-class.html#module,Variable pybindgen.enum.Enum.module=pybindgen.enum.Enum-class.html#module,Variable pybindgen.function.Function.module=pybindgen.function.Function-class.html#module,Module pybindgen.module=pybindgen.module-module.html"><a title="pybindgen.container.Container.module
pybindgen.cppclass.CppClass.module
pybindgen.enum.Enum.module
pybindgen.function.Function.module
pybindgen.module" class="py-name" href="#" onclick="return doclink('link-4', 'module', 'link-4');">module</a></tt> <tt class="py-keyword">import</tt> <tt id="link-5" class="py-name" targets="Class pybindgen.module.Module=pybindgen.module.Module-class.html"><a title="pybindgen.module.Module" class="py-name" href="#" onclick="return doclink('link-5', 'Module', 'link-5');">Module</a></tt> </tt>
<a name="L677"></a><tt class="py-lineno">677</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-6" class="py-name" targets="Module pybindgen.function=pybindgen.function-module.html"><a title="pybindgen.function" class="py-name" href="#" onclick="return doclink('link-6', 'function', 'link-6');">function</a></tt> <tt class="py-keyword">import</tt> <tt id="link-7" class="py-name" targets="Class pybindgen.function.Function=pybindgen.function.Function-class.html"><a title="pybindgen.function.Function" class="py-name" href="#" onclick="return doclink('link-7', 'Function', 'link-7');">Function</a></tt> </tt>
<a name="L678"></a><tt class="py-lineno">678</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-8" class="py-name"><a title="pybindgen.typehandlers" class="py-name" href="#" onclick="return doclink('link-8', 'typehandlers', 'link-0');">typehandlers</a></tt><tt class="py-op">.</tt><tt id="link-9" class="py-name" targets="Module pybindgen.typehandlers.codesink=pybindgen.typehandlers.codesink-module.html"><a title="pybindgen.typehandlers.codesink" class="py-name" href="#" onclick="return doclink('link-9', 'codesink', 'link-9');">codesink</a></tt> <tt class="py-keyword">import</tt> <tt id="link-10" class="py-name" targets="Class pybindgen.typehandlers.codesink.CodeSink=pybindgen.typehandlers.codesink.CodeSink-class.html"><a title="pybindgen.typehandlers.codesink.CodeSink" class="py-name" href="#" onclick="return doclink('link-10', 'CodeSink', 'link-10');">CodeSink</a></tt><tt class="py-op">,</tt> <tt id="link-11" class="py-name" targets="Class pybindgen.typehandlers.codesink.FileCodeSink=pybindgen.typehandlers.codesink.FileCodeSink-class.html"><a title="pybindgen.typehandlers.codesink.FileCodeSink" class="py-name" href="#" onclick="return doclink('link-11', 'FileCodeSink', 'link-11');">FileCodeSink</a></tt> </tt>
<a name="L679"></a><tt class="py-lineno">679</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-12" class="py-name" targets="Module pybindgen.cppclass=pybindgen.cppclass-module.html"><a title="pybindgen.cppclass" class="py-name" href="#" onclick="return doclink('link-12', 'cppclass', 'link-12');">cppclass</a></tt> <tt class="py-keyword">import</tt> <tt id="link-13" class="py-name" targets="Class pybindgen.cppmethod.CppMethod=pybindgen.cppmethod.CppMethod-class.html"><a title="pybindgen.cppmethod.CppMethod" class="py-name" href="#" onclick="return doclink('link-13', 'CppMethod', 'link-13');">CppMethod</a></tt><tt class="py-op">,</tt> <tt id="link-14" class="py-name" targets="Class pybindgen.cppclass.CppClass=pybindgen.cppclass.CppClass-class.html"><a title="pybindgen.cppclass.CppClass" class="py-name" href="#" onclick="return doclink('link-14', 'CppClass', 'link-14');">CppClass</a></tt><tt class="py-op">,</tt> <tt id="link-15" class="py-name" targets="Class pybindgen.cppmethod.CppConstructor=pybindgen.cppmethod.CppConstructor-class.html"><a title="pybindgen.cppmethod.CppConstructor" class="py-name" href="#" onclick="return doclink('link-15', 'CppConstructor', 'link-15');">CppConstructor</a></tt> </tt>
<a name="L680"></a><tt class="py-lineno">680</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-16" class="py-name" targets="Module pybindgen.enum=pybindgen.enum-module.html"><a title="pybindgen.enum" class="py-name" href="#" onclick="return doclink('link-16', 'enum', 'link-16');">enum</a></tt> <tt class="py-keyword">import</tt> <tt id="link-17" class="py-name" targets="Class pybindgen.enum.Enum=pybindgen.enum.Enum-class.html"><a title="pybindgen.enum.Enum" class="py-name" href="#" onclick="return doclink('link-17', 'Enum', 'link-17');">Enum</a></tt> </tt>
<a name="L681"></a><tt class="py-lineno">681</tt>  <tt class="py-line"><tt class="py-keyword">from</tt> <tt id="link-18" class="py-name" targets="Module pybindgen.utils=pybindgen.utils-module.html"><a title="pybindgen.utils" class="py-name" href="#" onclick="return doclink('link-18', 'utils', 'link-18');">utils</a></tt> <tt class="py-keyword">import</tt> <tt id="link-19" class="py-name" targets="Function pybindgen.utils.write_preamble()=pybindgen.utils-module.html#write_preamble"><a title="pybindgen.utils.write_preamble" class="py-name" href="#" onclick="return doclink('link-19', 'write_preamble', 'link-19');">write_preamble</a></tt><tt class="py-op">,</tt> <tt id="link-20" class="py-name" targets="Function pybindgen.utils.param()=pybindgen.utils-module.html#param"><a title="pybindgen.utils.param" class="py-name" href="#" onclick="return doclink('link-20', 'param', 'link-20');">param</a></tt><tt class="py-op">,</tt> <tt id="link-21" class="py-name" targets="Function pybindgen.utils.retval()=pybindgen.utils-module.html#retval"><a title="pybindgen.utils.retval" class="py-name" href="#" onclick="return doclink('link-21', 'retval', 'link-21');">retval</a></tt> </tt>
<a name="L682"></a><tt class="py-lineno">682</tt>  <tt class="py-line"><tt class="py-keyword">import</tt> <tt id="link-22" class="py-name" targets="Module pybindgen.version=pybindgen.version-module.html"><a title="pybindgen.version" class="py-name" href="#" onclick="return doclink('link-22', 'version', 'link-22');">version</a></tt> </tt>
<a name="L683"></a><tt class="py-lineno">683</tt>  <tt class="py-line"> </tt>
<a name="L684"></a><tt class="py-lineno">684</tt>  <tt class="py-line"><tt class="py-keyword">import</tt> <tt class="py-name">logging</tt> </tt>
<a name="L685"></a><tt class="py-lineno">685</tt>  <tt class="py-line"><tt class="py-comment">#logging.basicConfig(level=logging.DEBUG)</tt> </tt>
<a name="L686"></a><tt class="py-lineno">686</tt>  <tt class="py-line"><tt class="py-keyword">del</tt> <tt class="py-name">logging</tt> </tt>
<a name="L687"></a><tt class="py-lineno">687</tt>  <tt class="py-line"> </tt><script type="text/javascript">
<!--
expandto(location.href);
// -->
</script>
</pre>
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